refactor: move CloudEvents config to code constants

CloudEvents envelope format is protocol-level (not operator config).
When using DB config source without TOML, wrap_event() now uses
DEFAULT_CLOUDEVENTS_CONFIG from cloudevents_constants.py.

Changes:
- Add cloudevents_constants.py with DEFAULT_CLOUDEVENTS_CONFIG
- Update wrap_event() to accept Config, CloudEventsConfig, or None
- Simplify supervisor: always use wrap_event (has defaults)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/central/cloudevents_constants.py

@@ -0,0 +1,17 @@
+"""CloudEvents configuration constants.
+
+These defaults are used when no TOML configuration file is available
+(e.g., when using database-backed configuration source).
+
+These values are baked into the code because CloudEvents envelope format
+is part of the Central protocol contract, not operator-configurable.
+"""
+
+from central.config import CloudEventsConfig
+
+# Default CloudEvents configuration - used when TOML is unavailable
+DEFAULT_CLOUDEVENTS_CONFIG = CloudEventsConfig(
+    type_prefix="central",
+    source="central.echo6.co",
+    schema_version="1.0",
+)

src/central/cloudevents_wire.py

@@ -1,30 +1,48 @@
 """CloudEvents wire format helpers."""
 
-from typing import Any
+from typing import Any, Union
 
 from cloudevents.v1.http import CloudEvent
 
-from central.config import Config
+from central.config import Config, CloudEventsConfig
+from central.cloudevents_constants import DEFAULT_CLOUDEVENTS_CONFIG
 from central.models import Event
 
 
-def wrap_event(event: Event, config: Config) -> tuple[dict[str, Any], str]:
+def wrap_event(
+    event: Event,
+    config: Union[Config, CloudEventsConfig, None] = None,
+) -> tuple[dict[str, Any], str]:
     """
     Wrap an Event into a CNCF CloudEvents v1.0 JSON envelope.
 
+    Args:
+        event: The event to wrap
+        config: Either a full Config object, a CloudEventsConfig object,
+                or None to use defaults.
+
     Returns:
         A tuple of (envelope_dict, msg_id) where msg_id is the
         CloudEvent id for use as Nats-Msg-Id header.
     """
+    # Resolve CloudEventsConfig from various input types
+    if config is None:
+        ce_config = DEFAULT_CLOUDEVENTS_CONFIG
+    elif isinstance(config, CloudEventsConfig):
+        ce_config = config
+    else:
+        # It's a full Config object
+        ce_config = config.cloudevents
+
     # Build CE type: {prefix}.{category}.v1
-    ce_type = f"{config.cloudevents.type_prefix}.{event.category}.v1"
+    ce_type = f"{ce_config.type_prefix}.{event.category}.v1"
 
     # Serialize event data
     event_data = event.model_dump(mode="json")
 
     # Build extension attributes - lowercase, no underscores per CE spec
     extensions: dict[str, Any] = {
-        "centralschemaversion": config.cloudevents.schema_version,
+        "centralschemaversion": ce_config.schema_version,
         "centralcategory": event.category,
     }
 
@@ -36,7 +54,7 @@ def wrap_event(event: Event, config: Config) -> tuple[dict[str, Any], str]:
     ce = CloudEvent(
         attributes={
             "id": event.id,
-            "source": config.cloudevents.source,
+            "source": ce_config.source,
             "type": ce_type,
             "time": event.time.isoformat(),
             "datacontenttype": "application/json",